前身誌

爬虫両棲類学雑誌 Vol. 18(1999) No. 2

Hibernation sites of the tree frog, Rhacophorus schlegelii, were studied in the Nobi District of Miura Peninsula, central Japan, in the winter of 1997-1998. Twenty six frogs were detected hibernating in upper layers (x±SD=3.1±1.6cm in depth) of the soil at particular spots located at the edge of permanent ponds and in the banks of small streams at the headwaters. Soil conditions at the hibernating spots were characterized by low hardness, high water content, a lack of thick litter layer, and constantly cool temperature. In laboratory experiments, the frogs also showed clear preference for the soft and wet soil. Laboratory experiments together with field observations indicate that R. schlegelii selects particular places for hibernation in the soil to facilitate absorbing water and to reduce evaporative body water loss during dry winter on the Pacific coast of central Japan.

Antipredator and tongue flicking responses of hatchlings of Eumeces okadae were compared between Kozu-shima Island, where they co-occur with snake predators, and Hachijo-kojima, a snake-free island. In Experiment 1 lizards from both islands showed higher tongue flick rates to cotton swabs bearing snake and prey chemicals than to controls. Lizards from Hachijo-kojima emitted more tongue flicks to snake chemicals than those from Kozu-shima. In Experiment 2 lizards from Hachijokojima showed higher tongue flick rates to cotton swabs bearing non-saurophagous, allopatric snake chemicals than to control stimuli. Lizards from Kozu-shima exhibited tail wave display, which may deflect attacks to the autotomous tail, more frequently to saurophagous snake chemicals than to non-saurophagous snake and control stimuli, but there were no significant differences in tongue flick rates among the three chemicals for these lizards. In Experiment 3 lizards were introduced into an unfamiliar terrarium treated with snake chemicals. Lizards from Hachijo-kojima emitted more tongue flicks in cages chemically labelled by snakes than in control cages. No significant differences were observed in tongue flick rates between snake labelled and control cages in Kozu-shima lizards, and their tongue flick rates in snake labelled cages were significantly lower than those of Hachijo-kojima lizards. There were no differences in the frequency of tail waves, wall-climbing, movements, or immobility between snake labelled and control cages in lizards from both islands. Based on the higher tail wave frequency and lower tongue flick rates in Kozu-shima lizards than in Hachijo-kojima lizards, we hypothesize that lizards from Kozu-shima have evolved the ability to recognize chemical cues from snake predators after a few tongue flicks and that the higher tongue flick rates by lizards from Hachijo-kojima indicate less efficient recognition or lack of recognition of predator chemicals.

The spatial distribution pattern and associated social interactions of Oplurus cuvieri cuvieri were studied in a deciduous dry forest of Ampijoroa, Madagascar. Home range sizes were significantly larger in males than in females. In both sexes, snout-vent length was not correlated with home range sizes. Home range of males overlapped both inter- and intrasexually. Female home ranges rarely overlapped intrasexually. Consexual aggressive interactions indicated the presence of territoriality. Distribution pattern and observed intersexual interactions suggested a polygynous mating system. Site fidelity was observed for both home range and shelter tree levels. Tail breakage was moderately frequent, implying high predation pressure and the importance of safety refuge. No sexual differences were observed in thermal environment, perch height, or perch diameter, whereas sexual dimorphism in body size and dorsal color pattern was found. More than 80% of the lizards of both sexes performed “resting”.